Lead sharpener



Aug. 20, 1957 M. GEORGES LEAD SHARPENER 2 Sheets-Sheet 2 Filed June 24,1953 I 13 anes l United States. Patent 2,803,220 LEAD SHARPENER MichaelGeorges, Norw-ood, Mass.

I Application June 24, 1953, Serial No. 363,726

16 Claims. (Cl. 120-96) This invention relates to" means for sharpeningthe leads of pencils and is particularly concerned with the sharpeningof the leads now used in so-called lead holders or refill drawingpencils.

As is well known, hand driven and motor driven pencil sharpeners are oldin the art. At the present time, the most commonly used pencilsharpeners for sharpening wood encased leads are hand driven and suchsharpeners are satisfactory for the ordinary purposes to which woodpencils are put.

In recent years mechanical pencils have been developed in which theholder is of permanent character having means therein for causing thelead to be progressively moved outwardly from the holder as the lead isused. Such mechanical pencils include those utilizing large diameterleads which are generally used by draftsmen,

the approximate dimensions of the commonly used sizes being .078"diameter by 5%" in length. The leads of I mechanical pencils cannot besharpened by that type of sharpener used in sharpening ordinary leadpencils having the wood encased leads.

In drafting and stenographic work, fine-lines are used and accordinglyit -will be understood that the lead must be repeatedly sharpened. Notonly must the lead be sharpened, but it must be wiped after eachsharpening inorder to-insure that no carbon particles fall on thedrawing or drawing equipment to cause smudges;

Due to the difiiculty of sharpening a long unsupported lead point bymechanical means, the customary practice today still involves the useof. sandpaper lead pointers or metal files, both of which leaveweakening ridges in the lead. Also inlimited use is a small handsharpener into which the lead point is inserted, the hand sharpenerbeing rotated back and forth until a point has been produced. Thesharpener just described utilizes sharpening blades which converge to apoint and correspondingly when a lead has been sharpened by thismeans,the end of the lead will be literally pointed, but such point isinsufiicient in structural strength to standany use by the draftsman.That is, as soon as the draftsman attempts to utilize a lead sharpenedto this extent, the fine point will break off under normal use leavinga' somewhat enlarged rough point which when smoothed up slightly, maythen be put to satisfactory use by the draftsman.

The use of the hand sharpener is slow, and the subsequent breaking otfof the fine point produced thereby is troublesome when it occurs on thedrawing and accordingly it. is the practice among draftsmen aftersharpening the lead according to the best known methods available, topurposely break off the small weak portion 'of the point before puttingthe pencilto use. In addition,

the lead. a

With the foregoing disadvantages of existing practices in mind, it is anobject of this invention to provide a lead sharpener which will producequickly a finished, longer lasting, ready to use point on the lead of amechanical pencil without the utilization of any judgment or skill bythe operator.

It is a further object of this invention to provide a pencil sharpenercapable of functioning in such manner that the end of the sharpenedportion of the lead will not terminate in a point but rather at asection of small diameter and preferably slightly rounded and capable ofproducing a satisfactory line and of sufiicient structural strength toavoid breakage when initially used.

Another object of the invention is to provide a pencil sharpener sodesigned that after the sharpening has been completed, furtherunnecessary grinding away of the lead will be prevented. That is to say,once the lead has been sharpened to the maximum extent, sharpening willcease and cannot be resumed until the end of the lead has been worn orbroken away.

Another object of the invention is to provide means automaticallyoperable as the sharpening proceeds to throw the removed carbonparticles away from the point into a dust collecting unit so that whenthe sharpened lead point is removed from the sharpener, it will be freeof carbon dust particles to such extent that it may be used withoutbeing wiped, and without fear of smudges developing on the drawing fromunremoved carbon particles.

Another object of the invention is the provision of a cutting head ofsmall moment of inertia permitting greater usable cutting torque, theuse of a smaller motor and more rapid getting up to speed.

Still another object of the invention is to provide electricallyoperated means for driving the lead sharpener which may be readilyswitched on and of when the device is to be used and which at the sametime will be freely portable so that the collected dust particles may beemptied therefrom periodically.

These and other objects of the invention will become more apparent asthedescription proceeds with the aid of the accompanying drawings inwhich,

Fig. 1 is a plan view of the complete unit.

Fig. 2 is a front elevation of Fig. 1.

Fig. 3 is a section drawn to enlarged scale taken on the line 3-3 ofFig. 1.

Fig. 4 is a section on the line 4-4 of Fig. 5.

Fig. 5 is a vertical section of the cutter unit drawn to enlarged scaleand taken substantially on the line 55 of Fig. 4.

Fig. 6 is a horizontal section taken on the line 66 of Fig. 5.

Fig. 7 is a section takenon the line 77 of Fig. 8.

Fig. 8 is a vertical section of a cutter drawn to enlarged scale showinga modified construction and taken substantially, on the line 88 of Fig.7.

Fig. 9 is a'horizontal section taken on the line 9-9 of Fig. 8.

Fig. 10 is a vertical section of the base of the cutting blades mountedin a modified type of blade holder.

Fig. 11 is a horizontal section on the line 11-11 of Fig. 10.

Fig. 12 is a perspective view drawn to reduced scale showing one form ofconvenient means for securing the complete unit shown in Figs. 1, 2 and3 on a draftsmans table or other surface.

Referring first to Figs. 1, 2 and 3, the complete motor driven leadsharpener and cleaner comprises a box-like 3 metal housing 2 whichincludes a top cover plate 4 to which is afiixed a lead dust receptacle6 secured by the screws 8 passing through the horizontally extendingears 10, the vertical portions 12 of which are glued or otherwisesecured to the receptacle 6.

Mounted within the housing 2 is an electric motor 14 preferably of thephonograph type. This motor is low in cost, readily available arid runsat a speed suitable to drive the lead sharpener at the correct R. P. M.Motor 14 is affixed to a plate 4. Another plate 16, carrying electricalconnections is secured by the bolts 18 to one end of housing 2. Anexternal electrical connection 20 brings the necessary electric currentto the motor connections on plate 16. The motor includes a lower shaftbearing 22 and an upper bearing '24.

The motor shaft 26 extends upwardly from the motor through a felt padseal 28 into the lead powder receptacle 6. On the upper end of shaft 26is mounted the cutting head 30. The construction of this cutting headwill be described in more detail hereinafter.

Actuation of the motor 14 is controlled by a conventional electricswitch 32. Rubber feet 34 secured to the bottom of the casing 2 serve tocushion and anchor the unit in conventional manner.

The cutting head 30 which is mounted on the upper end of shaft 26 willnow be described. Referring first to Figs. 4, and 6, it will be seenthat there is a blade retainer 36 threaded axially at 38 and screwed onthe threaded end 40 of shaft 26. A lock nut 41 shown in Fig. 3 may beused if desired. The cylindrical portion of retainer 36 terminates at 42and thereabove consists of four pie shaped segments 44, 46, 48 and 50.Inserted between these segments are four identical cutting blades 52,54, 56 and 58 preferably made of hard tool steel. As can be seen in Fig.6, the interior vertical surfaces of the lower portions of these bladesterminate in surfaces at right angles to each other which enables thefour blades to fit closely together as shown.

By reference to Figs. 4 and 5 further details of the construction of thecutting blades will be better understood. The view shown in Fig. 5 istaken substantially along the line 5-5 of Fig. 4 with blade 56 removedin its entirety. As all of the blades are identical a description of onewill suffice for all. Referring particularly to blade 58 shown in Figs.4 and 5, it will be seen that there is a horizontal shelf 60 with itsexterior edge at right angles from which extends upwardly the cuttingedge 62 bounded by the sides 64 and 66. The included angle between theblade faces 64 and 66 is preferably between 60 and 70 as it has beenfound that this gives a satisfactory scraping action on the lead. Theother cutting edges on the other blades are designated as follows: Blade52 has edge 68, blade 54 has edge 70 and blade 56 has edge 72. The shelf60 of blade 58 has its counter parts at 74 in blade 52, at 76 in blade54, and at 78 in blade 56. These four shelves come together to form ahorizontal surface which is 'a plane in which the lower ends of thecutting edges 62, 68, 70 and 72 terminate. As can be seen in Figs. 4 and5, the cutting edges do not come to a point, but rather terminate in theplane of the shelves to leave a space 80 which constitutes the minimumdiameter to which the end of the lead may be sharpened.

Those portions of the blades that are above the tops of the pie shapedsegments 44, 46, 48 and 50, which tops are indicated at 82, are spacedapart at 90 so that any lead removed in the sharpening can be thrown outradially to be collected in the lead powder receptacle 6. By varying thedimension 80, which is the distance between the lower ends of each pairof opposed edges of the cutting blades, the minimum diameter of the endsof the lead may be controlled. The included angle between the cuttingedges 62 and 70 and between 68 and 72 is preferably between and Byvarying this angle as desired through the use of other sets of cutters,the conical formation of the point may be changed from sqms b un to a 9.1% fiBQE:

Secured to the top ends of the four cutting blades is a lead guide 84.This consists of a circular body portion 86 having a hemisphericaldepression 88 and a central lead receiving aperture 90. Extendingdownwardly from the under side of the lead guide are four pie shapedfeet shown in Fig. 4 at 92, 94, 96 and 98 which sections fit between theupper ends of blades 52, 54, 56 and 58. The lead guide may be secured inposition by cementing the feet to the blades, or brazing the partstogether.

It will be understood that all of the parts thus described are assembledin concentric fashion with the center line of shaft 26 coinciding withthe center line of blade retainer 36, the center line forming thejunction of the four blades and the center line of opening of the leadguide. The parts are also dynamically balanced so that upon rotation ofshaft 26, the entire cutting head will rotate smoothly along the axis ofshaft 26 as extended.

From the description given thus far, it is believed that the operationof the unit may now be clearly understood. The user starts the cuttinghead 30 rotating by pressing the switch 32 of the motor putting thelatter in operation. Enough of the lead of the mechanical pencil to besharpened is exposed so that the body of the pencil will not come intoengagement with the lead guide. The lead is then inserted downwardlythrough hole 90, this hole being large enough to take the largest of theconventional sized leads. As the lead moves downwardly, the end comesinto engagement with the rotating cutting edges of the blades whichassists the lead guide in directing the lead to a vertical position sothat it will be truly centered with respect to the rotating cutter. Thelead particles as fast as they are shaved from the surface to the leadare thrown radially outward away from the cutting blades to be collectedin the bottom of the lead powder receptacle 6. As the cutting away ofthe lead proceeds, the lead moves downwardly within the confines of thefour rotating cutting edges, 62, 68, 70 and 72 until the end of the leadengages the bottom formed by the horizontal shelf surfaces at the lowerends of the cutting edges. Further downward movement of the lead is thusprevented and the point at this time is in complete sharpened condition.It is then removed upwardly and withdrawn from the lead guide. The motormay then be shut off to stop the rotation of the cutting head and theoperation is complete.

Upon examination of the point produced by this mechanism, it will beseen that the end is circular and not pointed. The diameter of thecircular end is equal to the distance 80 which in a preferred form hasbeen found to be approximately .016 inch. This dimension is small enoughto give a sharp line suitable for drafting purposes, and at the sametime, the lead is strong enough to withstand breakage under thepressures that would normally be applied. Furthermore, an examination ofthe surface of the lead point will show that it is substantiallycompletely free of all loose carbon particles, and therefore, does notneed to be wiped prior to use. That is to say, the point produced bythis device is ready for immediate use and accordingly in the course ofa day, a substantial amount of time is saved by the user in thesharpening of leads.

A modified form of cutter head is shown in Figs. 7, 8 and 9. Thedifference over Figs. 4, 5 and 6 resides principally in the bladeconstruction. The edges of the abutting lower vertical portions of theblades which in this modification are numbered 100, 102, 104 and 106 areground away to present flat surfaces 108, 110, 112 and 114. Thus, whenthe blades are assembled, there is a square vertical hole at thejuncture of the four blades. In this hole is placed and secured a wire116 with its upper end preferably located at the lower ends of thecutting edges of the blade. A hole 118, concentric with the center lineof the blades, is provided in the upper end of blade holder 120 whichwill permit insertion of the wire to proper position. The pie shapedsegments that support the lower ends of the blades and which arenumbered 122, 124, 126 and 128 act in the same manner as segments 44,46,48 and 50of Figs. and 6. The cutting headf30 of Figs. 7, 8 and 9operates in the same manner as that explained above in connection withFigs. 4, 5 and 6.

A slightly different type of blade retainer is shown in Figs. and 11. Inthis form the blade retainer 130 is formed with a cylindrical opening132 in its top end. Into this opening the four blades 134, 136, 138 and140 are inserted as shown in Fig. 11, making a forced fit therein. Theinner right angled surfaces of the blades abut and with the help of theretainer wall are held in correct aligned position. These blades may bethe same as those disclosed in Figs. 4, 5 and 6, but, as shown, are thesame as in Figs. 7, 8 and 9 and accordingly a wire 142 fills the centralopening and provides the surface which the lead engages after it hasbeen sharpened to the maximum extent.

Fig. 12 illustrates a simple way of mounting the sharpener on a desk. Abracket 144 has screw holes 146 permitting the face 148 to be screwed tothe table. The other face 150 has four headed projections 152 adapted tohold vertically the wall 154 of the housing 2 by means of the invertedkey hole openings 156. See Fig. 2. In this way the entire unit may beremoved and inverted to dump the collected lead dust from the leadpowder receptacle 6.

It will be understood, of course, that the receptacle 6 could be maderemovable from the casing 2 so that it would not be necessary to disturbthe motor and cutting head when emptying the receptacle. However, in mypreferred form, I have found it more convenient to have the receptacleintegral with the casing as it is thereby possible to have a moresecure, rigid unit which is not inconvenient to lift in its entirety andturn up-side-down to empty the lead powder receptacle.

It is my intention to cover all changes and modifications of the exampleof the invention herein chosen for purposes of the disclosure which donot constitute departures from the spirit and scope of the invention.

I claim:

1. A lead sharpener comprising a rotatable cutting head including incombination a blade retainer, a plurality of radially arranged cuttingblades mounted on said retainer, said blades being spaced from eachother to provide egress therebetween of shavings removed by said blades,the cutting edges of said blades converging and defining a pyradmidalspace therebetween to receive the lead of a pencil, the lower ends ofsaid cutting edges terminating in spaced apart relation, a lead guideaffixed to the upper ends of said blades, said lead guide having anopening therein concentric with said blades and a substantial depressionin its upper surface with sides sloping toward said opening whereby thelead of a pencil can be introduced into said pyramidal space, and meansfor preventing the downward movement of a lead being sharpened below thelower ends of the edges of said blades.

2. A lead sharpener as set forth in claim 1, said means for preventingthe downward movement of the lead that is being sharpened, comprising awire concentrically aligned with said blades.

3. A lead sharpener as set forth in claim 1, the cutting edge of eachblade terminating at its lower end adjacent a horizontal shelf that isintegral with said blade.

4. A lead sharpener as set forth in claim 1, the lower inner verticalportions of said cutting blades below said cutting edges having engagingfaces, the sum of the included angles between the said faces of all ofthe blades equaling 360.

5. A lead sharpener as set forth in claim 1 and comprising in additionan electric motor, a vertical shaft driven by said motor, said rotatablecutting head mounted on said shaft, a lead powder receptacle above saidmotor surrounding said cutting head and part of said shaft and means forpreventing lead powder that may be in said lead powder receptacle fromreaching the bearings of said shaft.

6. A lead sharpener as set forth in claim 1 in which the diameter of theopening of said lead guide is not greater than the diameter of thegenerated circumference of the upper ends of said blades.

7. A lead sharpener comprising a rotatable cutting head including incombination a blade supporting member,

a plurality of radially arranged blades of which at least one has .acutting edge mounted on said member, said blades being spaced from eachother to provide egress therebetween of shavings removed by said blade,the said blades converging and defining a pyramidal space therebetweento receive the lead of a pencil, the lower ends of said bladesterminating in spaced apart relation, a lead guide above the cuttingedges of said blades, said lead guide having an opening thereinconcentric with said blades whereby the lead of a pencil can beintroduced into said pyramidal space, and a stop for terminatingdownward movement of said lead at a predetermined level.

8. A lead sharpener as set forth in claim 7, said stop comprising a wireconcentrically aligned with said blades.

9. A lead sharpener as set forth in claim 7 and comprising in additionan electric motor, a vertical shaft driven by said motor, said rotatablecutting head mounted on said shaft, a lead powder receptacle above saidmotor surrounding said cutting head and part of said shaft, and

means for preventing lead powder that may be in said lead powderreceptacle from reaching the bearings of said shaft.

10. A lead sharpener as set forth in claim 7 in which the diameter ofthe opening of said lead guide is not greater than the diameter of thegenerated circumference of the upper ends of said blades.

11. A lead sharpener as set forth in claim 7 each blade terminating atits lower end adjacent a horizontal shelf that is integral with saidblade.

12. A lead sharpener as set forth in claim 7 the lower inner verticalportions of said blades below said cutting edges having engaging faces,the sum of the included angles between the said faces of all of theblades equalling 360.

13. A lead sharpener as set forth in claim 7, each of said bladesincluding a portion extending below the apex of said pyramidal space,each portion having two vertical beveled edges with each beveled edge ofone portion in engagement with the adjacent corresponding beveled edgeof the next portion, the junction of said beveled edges of each portionbeing flattened thereby to provide a vertical opening between saidportions.

14. A lead sharpener comprising a motor, a vertical shaft driven by saidmotor, a rotatable cutting head mounted on the upper end of said shaft,said cutting head including a plurality of blades at least one of whichhas a straight cutting edge, said blades fixed with respect to eachother and to said shaft and spaced apart sufficiently to permit leadparticles ground from said lead to be thrown by centrifugal forcelaterally of said blades, a lead powder receptacle above said motor andsurrounding said cutting head for receiving said lead particles, a leadguide mounted independently of said receptacle and fixed with respect tosaid cutting head and rotatable therewith whereby a lead to be sharpenedmay be directed properly to said blades.

15. For use in a lead sharpener, a cutting blade having an upper slopingportion including a cutting edge, a portion below said cutting edge withvertical bevelled edges, the junction of said bevelled edges beingflattened thereby to provide a vertical opening between a plurality ofsaid blades when said blades are in engagement along their verticalbevelled edges.

16. For use in a lead sharpener, a cutting blade having an upper slopingportion including a cutting edge, a portion below said cutting edge withvertical bevelled edges and a shelf-like structure extending away fromthe lower end of said cutting edge to act as a lead stop.

References Cited in the file of this patent UNITED STATES PATENTS GayOct. 4, 1887 Hager et a1. May 21, 1912 Burdick June 27, 1922 FischerDec. 14, 1926 10 Benczalski Nov. 4, 1930

